Mechanical interlock



Oct. 10, 1950 3 Sheets-Sheet 2 Filed June 19, 1948 Fig.4.

3 0 5 1- 5 A. 1 R z J 3 U 3 .7 k l Z A Mfl M 3 1 L #1 6 z I lNVENTOROWEN L.TAYLQR.

BY M 6. M &

ATTORNEY Oct. 10, 1950 Filed June 19, 1948 WITNESSES A famio. 1.. TAYLORMECHANICAL m mawgix 3 Sheets-Sheet 3 H 7 llllllllllllmllllllllll l'l Elimmuuuumn KNVENTOR OWEN L. TAYLOR.

BY v

ATTORNEY Patented Oct. 10, 1950 UNITED STATES PATENT OFFICE MECHANICALINTERLOCK Application June 19, 1948, SerialNo. 34,036

((11. Tie-483) 10 Claims.

This invention relates, as indicated, to a mechanical interlock forinterlocking the operation of two relatively movable members and, moreparticularly, to an improved arrangement of in terlocking mechanism fora pair of electromagnetically operated switches controlling reversing ormultiple speed electrical connections to a, motor.

The switches on reversing or multiple speed contactors must beinterlocked in order to prevent the completion of a circuit through,more than one switch at any given instant. This requires that anoperating circuit through the contacts on one of the switches must beopen before a circuit can be established through the contacts on anotherswitch. The interlock must not only be capable of preventingsimultaneous physical contact engagement in more than one switch, but inaddition must be effective to prevent contact engagement by a secondswitch prior to extinguishment of the are drawn by the contacts of theswitch being opened. Premature contact engagement of the switch beingclosed before extinguishment of the arc drawn by the switch being openedwould otherwise result in a short circuit. The problem of prevent ingsuch premature contact engagement is rendered difficult by relays ofmodern design due to their design tendencies toward small moving partshaving low inertia, the use of high-speed magnets with small magnettravel, and a smaller open gap distance between the stationary andmovable contacts.

Generally stated, the problem of arc extinguishment may be taken care ofby an interlock which will operate to effect movement of one set ofswitch contacts to their full open position as determined by their opengap distance before allowing the other set of switch contacts to movesubstantially out of full open position Such interlocks have approachedthis problem by causing the difierent sets of contacts to move .atunequal rates of travel whereby those opening are moved initially at ahigh rate of speed into substantially full open position while thoseclosing move at a relatively slow rate of speed only a small distance oftheir total travel from full open position. However, interlocks designedalong this line have run into a condition known as jamming which iscaused by the interlock op- ,eratin to hold a first switch in its closedposition in response to force applied thereto upon energization of amagnet operating coil for a second switch. This condition will cause theoperating coil for the second switch to fail in 2 a short period of timeif it is maintained energized.

One of the principal objects of this invention is to, provide animproved arrangement of interlocking mechanism for a pair ofelectromagnetically operated switches which is efi'ective to preventcompletion of a circuit through both of the switches under anycondition, and which will accomplish its function without jamming theop: eration of either of the switches.

A further object of this invention is to provide interlocking mechanismfor a pair of electromagnetically operated switches which iseffective-to maintain one of the switches sub stantially in its fullopen position until such time as the other of the switches moves to itssubstantially full open position.

A still further object of the invention is to provide interlockingmechanism for a pair of electromagnetically operated switches which willoperate to lock one of the switches in its full open positionimmediately upon movement of the other of the switches out of its fullopen position.

Another object of the invention is to provide a simplified arrangementof interlocking mechanism which may be produced at a minimum of cost andwhich will operate indefinitely without failure.

Another object of this invention is to provide an improved arrangementof interlocking mechanism in which the interlocking action is providedby a pair of locking links connected together for angular movementrelative to each other and having operating connections respectivelywith the moving parts which they operate to interlock.

Another object .of this invention is to provide interlocking mechanismof the character just referred to in which the common connection for thelocking links is provided by a fiat leaf spring having knife edge,engageable in V-shaped notches formed in the locking Gther objects andadvantages of this invention will become apparent from the followingdescription.

In the drawings there are shown several embod-iments of the invention.In this showing:

Figure 1 is a plan view, with parts thereof being shown in section, of apair of electromagnetically operated switches illustrating theapplication thereto of a preferred embodiment of interlockin mechanismconstructed in accordance with the principles of this invention;

Fig. 2 is a partial plan view, similar to Fig. 1,

showing the position of the interlocking mechanism when one of theswitches is in its closed position;

Fig. 3 is a view similar to Fig. 2, showing the position of theinterlocking mechanism when the other of the switches is in its closedposition;

Fig. 4 is a bottom plan view of the interlocking mechanism shown inFigs. 1, 2 and 3;

Fig. 5 is a side elevational view looking from the right of theinterlocking mechanism shown in Fig. 4;

Fig. 6 is a plan view of a modified form of interlocking mechanism;

Fig. '7 is a plan view of a pair of verticallyspacedelectromagnetically-operated switches illustrating the applicationthereto of interlocking mechanism constructed in accordance with theprinciples of this invention;

Fig. 8 is a broken away side elevational view of the interlockingmechanism shown in Fig. 7 looking from the right;

Fig. 9 is a view similar to Fig. 8 looking from the left of theinterlocking mechanism; and

' Fig. 10 is a view similar to Fig. 8 illustrating a difierent positionof the interlocking mechanism.

The preferred embodiment of the invention is shown in Figs. 1 through 5.Referring to Fig, 1, the numeral 1 designates a support on which ismounted in horizontally spaced relation a pair of electromagneticallyoperated switches indi- 1*:

cated as a whole by the numerals 2 and 3. Each of the switches 2 and 3is provided with an insulated housing or arcing chamber 4 containing aset of stationary contacts 5 and a set of movable contacts 6. mounted ina conventional manner on a movable contact carrying member I formovement from the full open position shown in Fig. l to a closedposition in which the stationary contacts 5 are electrically engagedwith the movable Contact ii. The movable contact carrying parts I of theswitches 2 and 3 are provided respectively with operating parts 8 and 9which are movable in parallel paths for effecting movement of therespective switches to circuit completing positions. Operation of eachof the operating parts 8 and 9 is efiectedby an armature l8 constitutingpart of an electromagnet l i having an energizing coil l2. Uponenergization of a selected one of the coils [2, its armature It] willoperate to move the operating part 8 or 9 to which it is connected in anupward direction, as viewed in Fig. move one of the switches 2 or 3 toits closed position.

Operation of the operating parts 8 and 9, and thereby the operation ofthe switches 2 and 3, is controlled by interlocking mechanism indicatedas a. whole by the numeral l3. As best shown in Figs. 4 and 5, theinterlocking mechanism l3 comprises a supporting bracket l4 having aback portion l5 by which it may be secured to the support I as by screws16. Projecting outwardly from the bracket portion I5 are a pair of legsI"! and 18 of unequal length. Bell crank levers l9-and 20 are connectedto the outer ends of the legs I! and 18 by pivots 2| and 22. The bellcrank 29 is provided with an outwardly projecting arm 23 having its endoperatively connected to the operating part 8 of a switch 2 so thatoperation of the switch 2 will be effective to impart pivotal movementto the bell crank 29. The bell crank I9 is similarly provided with anoutwardly projecting arm 24 which is operatively connected to theoperating part 9 of the switch 3 so that operation of the switch 3 WiEach set of movable contacts 6 is impart pivotal movement to the bellcrank 19. The bell cranks l9 and 29 are provided respectively with arms25 and 26 projecting inwardly toward each other and in overlappingrelation so that their respective ends 2! and 28 are positioned onopposite sides of a center line between the pivots 2| and 22. Lookinglinks 29 and 39 are connected respectively to ends 21 and 28 by pivots3| and 32. The lower ends of the locking links 29 and 39 are connectedtogether for angular movement relative to each other by a flat leafspring 33. As best shown in Fig. 5, the leaf spring 33 is L-shaped andhas a back portion 34 thereof anchored to the bracket 14 by means of aslot 35 formed in the bracket part l5 in which the one edge of the leafspring portion 34 is receivable. An end of the leaf spring portion 34 issecured to the bracket 14 by threaded fastening members 36. A flexibleportion 3'! of the spring 33 projects outwardly from its back portion 34to a position between the pivots 2i and 22 as best shown in Figs. 1through 3. A slot is formed in the upper edge of the flexible spring 31to provide a knife edge 38 which projects upwardly into the apex ofV-shaped notches 39 formed in the lower ends of the locking links 29 and30. The knife edge 38 on the flexible portion 31 of the spring 33 thusprovides a common connection for the links 29 and 30 at their lower endsabout which the links 29 and 39 may move relative to each other in amanner and for a purpose to be described.

Attention is particularly invited to the fact that the parts of theinterlocking mechanism l3 are symmetrically arranged with respect to theflexible spring 31 when both switches 2 and 3 are in the open positionas shown in Fig. 1. It will be noted in particular that the pivots 2|and 22, which form the fulcrums for the bell cranks I 9 and 20, arespaced equal distances from and on opposite sides of the flexible spring31 which can flex in a direction toward and away from such pivots. Itwill also be noted that the arms 23 and 24 extend in oppositedirections'to their points of engagement with the operating parts 8 and9 of the switches 2 and 3. It will also be noted that the unequal lengthof the parts I1 and I8 of the support M, as shown in Fig. 4, togetherwith the offset construction of the bell cranks enables the inwardlyprojecting arms 25 and 26 to overlap each other with their end points 21and 28 on opposite sides of the spring 33. The symmetrical arrangementis completed by the common connection provided by the knife edge 38 atthe lower ends of the locking links 29 and 30 which have their upperends pivoted at 3| and 32 to the ends 21 and 28 of the bell cranks I9and 28.

With both switches 2 and 3 in their full open position as shown in Fig.1, closure of either switch 2 or 3 may be readily effected byenergization of the appropriate magnet H. Assuming that the switch 2 isclosed by energization by its operating magnet H, the first action thatwill take place will be upward movement of the operating part 8 for theswitch 2. As the operating part 8 moves upwardly, the bell crank 20 willbe pivoted in a clockwise direction, and the end point 28 of its arm 26will move downwardly. As the endpoint 28 moves downwardly, the lockinglink 39 will operate t flex the spring 31 to the left, and such actionwill cause the locking link 29 to rotate in a clockwise direction. Whenthe switch 2 moves into its fully closed position, its operating part 8and the parts of the interlockin mechanism l3 will occupy the positionshown. in Fig. 2. In this position it will be noted that the lockinglink 29 is effective to prevent rotational movement of the bell crank[-9 in a counterclockwise direction and thus upward movement of theoperating part 9 for the switch 3. This locking action is due to themovement of the knife edge 38 to a position substantially underneath thepivot 3| as shown in Fig. 2. While this movement is taking place, thelink 29 is pivoting in a clockwise direction about its pivot 3|, andsuch pivotal movement takes place without any perceptible movement beingimparted to the bell crank $9. In addition, substantiall all of theflexing of the spring .31 and movement of the knife 38 to the left takesplace during the initial portion of the. closing movement of the switch2; At the moment the closing action begins to take place, it will benoted that pivot 32 will move downwardly toward the spring 3'! and itsknife edge 38, thus tending to shorten the distance between the pivot 32and the knife edge 33. This results in a rapid movement of the knifeedge 38 to the left from the position shown in Fig. 1, and the switch 2will have barely moved out of its open position when the locking link 29Will become operable to prevent movement of the bell crank l9 andconsequent movement of the switch 3 out of its full open position.During the final closing action of the switch 2 to the positioifihown inFig. 2, it will be noted that the pivot 32 is moving substantiallytangentially with respect to a circle having as its center the knifeedge 38. As a result there will be very little movement of the spring3'! during the final movement of the switch 2 to its closed position.

The above-described movements of the interlocking mechanism l3 must bereversed to return the parts to the position shown in Fig. 1 before theoperating part 9 may move upwardl to effect closing of the switch 3.This means that the operating part 8 for the switch 2 must be loweredfrom the position shown in Fig. 2, and during its initial movement verylittle movement of the knife edge 38 is permitted. Most of the flexingmovement of the spring 31 during the return of the knife edge 38 to itscenter position, as shown in Fig. 1, takes place during the final movment of the switch 2 to its full open position. It will thus be seenthat as the switch 2 moves into its full open position, the switch 3will still be in its full open position.

When the operating part 9 moves upwardly to effect a closing of theswitch 3, the parts of the interlocking mechanism I3 will move to theposi tion shown in Fig. 3. In this position the link 39 is operative toprevent clockwise movement of the bell crank 25 and upward movement ofthe operating part 8 to close the switch 2. The movement of the partsinto the position shown in. Fig. 3 is acomplished in the same manner andat the same rates of travel as described in connection with Fig. 2.

From the foregoing, it will be apparent that a small movement of eitherswitch toward its closed position will be effective to lock the other ofthe switches againstmovement to its closed position. It will also benoted that the switch which has moved toward or into its closed position must be returned to substantially its full open position before theother switch can move toward or into its closed position.

In addition to the action of the spring 3'! in cooperation with thelocking links 29 and 39 to insure movement of both switches to a fullopen position before either can be closed, it will be noted that thetension imparted to. the spring 31 by closure of one of the switches iseffective to produce a biasing force for returning a switch to its openposition upon deenergization. of its operating magnet l I. In the eventthat the operating magnet for a switch in open position is energizedprior to movement of the other position to its full open position, theclosing force applied by the magnet.v energized will. bev transmitted ina direction assisting the spring 31 in the return of the other switch toits full open position.

Referring to Fig. 2, it will be noted that the knife: edge 38. ispositioned slightly to the right of a position directly underneath thepivot 31. Referring to Fig. 3, it will be noted that the knife edge 38is positioned slightly to the left ofa positiondirectly underneath thepivot 32. The positions of the knife edge 38- illustrated respectivelyin Figs. 2 and 3 represent the extreme end portions of. the path ofmovement of the knife edge 38. By constructing the parts in such mannerthat the end points of the path of movement of the knife edge 38 aremaintained within the outer limits of the pivots 3i and 32, jammingaction by reason of energization of one of the operating magnets priorto deenergization of the other operatin magnet is effectively prevented.This action will be best understood by referring to Fig. 2 and assumingthat the magnet l I to the right of Fig. 2 is energized prior todeenergization of the magnet ll. Since. the knife edge 38 is positionedto the right of the pivot 3|, the force applied to the bell crank arm 24upon energization of the magnet to the right is applied to the bellcrank 20 through the interlocking mechanism 13 in a direction tending tomove the operating part 8 for the switch 2 down wardly and to its openposition. Consequently, upon deenergization of the magnet II, this forcewill be effective immediately to' open the switch 2 without any jammingaction tending to hold the switch in its closed position.

The modified form of interlocking mechanism illustrated in Fig. 6 isessentially the same as the interlocking mechanism shown in Figs. 1through 5, and like parts have been designated by like numerals. In thisconstruction, the common connection at the base of the links 29 and 3i!is provided by a, pivot pin 40 about which the links 29 and may moveangularly relative to.

each other. A roller M is carried by the pivot and is engageable with asurface 42 during the back and forth movement of the common connectionor pivot 40 between the pivots 2| and 22. The operation of thisstructure during opening and closing movements of a pair of switches issubstantially the same as that described in connection with Figs. 1through 3.

The modification, illustrated in Figs. 7 through 10, illustrates theapplication of interlocking mechanism, designated as a whole by thenumeral 50, and constructed in accordance with the principles of thisinvention, to a pair of switches 5| and 52 mounted in vertically spacedrelation and respectively having electromagnetically actuated operatingparts 53 and 54. The interlocking mechanism comprises a support 55 onwhich a pair of arcuately-shaped levers 58 and 57 are pivotally mountedrespectively by pivots 58 and 59. The arrangement of the pivots 58 and59 will be best understood by referring to Figs. 8 and 9 which show theinterlockin mech anism 50 from opposite sides thereof. As best shown inFigs. 7 and 8, the lever 56 is pivotally connected to an actuatingmember 60, which in turn is connected to a, vertically movable actuatingpart 6! of the switch 52. As best shown in Figs. 7 and 9, the link 51 ispivotally connected to a vertically movable operating part 62 of theswitch A locking link 63 is pivotally connected to the lever 58 and alocking link 64 is pivotally connected to the lever 51. l he links 63and 54 are provided with V-shaped notches 65 at their lower ends, and aknife edge 56 provided on a fiat leaf spring 51 extending transverselyof the levers 56 and 57 projects upwardly into the notches 65 to providea common connection at the lower ends of the locking links 63 and 64.

When both of the switches 5i and 52 are in their full open position, thelocking links 63 and 64 will be symmetrically arranged with respect tothe spring 61. Figs. '1, 8 and 9 show the relative positions of theparts with the lower switch 5| in a closed position. When the switch 5!moves to a closed position, the lever 51 moves upwardly about its pivotand causes the locking link 54 to move the spring 61 to the left asviewed in Fig. 8. With the locking link 63 in the position shown in Fig.8, the spring 81 will function to prevent upward movement of the link 63and pivotal movement of the lever 55 in a clockwise direction, as viewedin Fig. 8. Upward movement or the operating part 6| and consequentmovement of switch 52 to a closed position will thus be prevented.

Fig. illustrates the positions of the parts of the interlockingmechanism 55 when the operating part 6| has moved upwardly to close theswitch 52. When the operating part El moves upwardly to close the switch52, the lever 56 is pivoted in a clockwise direction, as viewed in Fig.10, and the locking link 63 moves the spring 6'! to the right as viewedin Fig. 10. In this position upward movement of the link 64 is preventedby reason of its engagement with the spring 61. Consequently, upwardmovement of the lever 51 and downward movement of the operating part 62connected to the magnet for the switch 5| is prevented, and closure ofthe switch 5! is likewise prevented.

In the arrangement shown in Figs. '7 through 10, the levers 55 and 51,together with the locking links 63 and 54, and the common connectionprovided by the spring 61 is effective to prevent movement of one of theswitches out of its full open position upon movement of the otherswitches toward or into its closed position. In addition, theinterlocking mechanism 5!) is effective to insure that the switch inclosed position is returned to its full open position before the otherswitch can be moved to its closed position.

Since certain changes may be made in the above-described constructionand different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all the mattercontained in the above description and shown in the accompanyingdrawings shall be considered as illustrative and not in a limitingsense.

I claim as my invention:

1. An interlocking mechanism comprising a pair of bell cranksrespectively having a fulcrum and a, pair of arms disposed in fixedrelative angular positions, said fulcrums being located at spacedpoints, one arm on each of said bell cranks projecting outwardly andeach being constructed and arranged to have a force applied thereto tomove the associated one of said bell cranks, the remaining arm of eachof said bell cranks extending inwardly toward the remaining arm of theother bell crank, the end points of the remaining arms lying inoverlapping relation to provide end points on opposite sides of acenter-line between said spaced fulcrums, a pair of locking links, eachof said end points on said remaining arms having a pivot to which one ofsaid links is connected, and a common connection interconnecting saidlinks for angular movement relative to each, said common connectionhaving a position located substantially centrally with respect to saidfulcrums prior to movement of either of said bell cranks.

2. An interlocking mechanism comprising a pair of bell cranksrespectively having a fulcrum and a pair ofarms, said fulcrums beinglocated at spaced points, one arm on each of said bell cranks projectingoutwardly and being constructed and arranged to have a force appliedthereto to move the associated one of said bell cranks, the remainingarm of each of said bell cranks extending inwardly toward the remainingarm of the other bell crank, the end points of the remaining arms lyingin overlapping relation to provide end points on opposite sides of acenterline between said spaced fulcrums, a pair of locking links, eachof said end points on said remaining arms having a pivot to which one ofsaid links is connected, and a flat leaf spring positioned centrally ofsaid bell cranks and mounted for flexing movement toward and away fromsaid fulcrums, each of said locking links having V- shaped notchesprovided therein, said spring having a knife edge projecting into saidnotches to provide a common connection about which said links may moveangularly relative to each other.

3. An interlocking mechanism comprising a pair of hell cranksrespectively having a fulcrum and a pair of arms, said fulcrums beinglocated at spaced points, one arm on each of said bell cranks projectingoutwardly and being constructed and arranged to have a force appliedthereto to move the associated one of said bell cranks, the remainingarm of each of said bell cranks extending inwardly toward the remainingarm of the other bell crank, the end points of the remaining arms lyingin overlapping relation to provide end points on opposite sides of acenter-line between said spaced fulcrums, a pair of locking links, eachof said end points on said remaining arms having a pivot to which one ofsaid links is connected, a common pivot interconnecting said links forangular movement relative to each other, said pivot being located anequal distance from each of said end points, a roller carried by saidpivot, and a support having a surface extending between said fulcrumswith which said roller is engageable.

4. An interlocking mechanism for a pair of levers for locking one leverupon movement of the other which comprises a pair of pivotally mountedlevers, a pair of locking links, each of said links having a separatepivotal connection to one of said levers, and a flat leaf springpositioned between said levers, each of said locking links havingV-shaped notches provided therein, said spring having a knife edgeprojectin into said notches to provide a common connection about whichsaid links may move angularly relative to each other.

5. An interlocking mechanism for a pair of levers for locking one leverupon movement of the other which comprises a pair of levers respectivelyhaving a pivot mounting, said pivot greater 9 mountings being located atspaced points, said levers extending toward each other and inoverlapping relation from their respective pivot mountings and havingend points positioned on opposite sides of a center-line between saidmountings, a pair of locking links, each of said end points having oneof said links pivotally connected thereto, and a common connectionconnecting said locking links for angular movement relative to eachother, said common connection being located substantially centrally ofsaid pivot mountings priorto movement of either'of said levers, pivotalmovement of one of said levers being effective through the locking linkconnected thereto and said common connection to move the other of saidlocking links into a locking position with respect to the other of saidlevers to prevent movement of the other of said levers.

6. An interlock for a pair of relatively movable members operable tolock one of said members against movement in response to movement of theother of said members which comprises pair of levers respectively havinga pivot mounting and a connection operable to effect pivotal movementthereof in response to movement of one of said members, a pair oflocking links, each of said levers having one of said locking linkspivotally connected thereto, and a fiat leaf spring mounted for flexingmovement between said levers, each of said links being provided with aV-shaped Y notch, said spring having a knife edge projecting into bothof said notches to provide a common connection between said links aboutwhich they may move angularly relative to each other, pivotal movementof one of said levers in response to movement of one of said membersbeing effective through the locking link connected thereto and saidcommon connection to move the other said links into a locking positionwith respect to the other of said levers for preventing movement of theother of said levers.

'7. An interlock for a pair of relatively movable members operable tolock one of said members against movement in response to movement of theother of said members which comprises a pair of levers respectivelyhaving a pivot mounting and a connection with one of said members sothat movement of either of said members will impart pivotal movement toone of said levers, said pivot mountings being located at spaced points,said levers extending toward each other and in overlapping relation fromtheir respective pivot mountings and having end points positioned onopposite sides of a center-line between said pivot mountings, a pair oflocking links, each of said end points having one of said locking linkspivotally connected thereto, and a common connection connecting saidlinks for angular movement relative to each other, said commonconnection being located'substantially centrally of said pivot mountingsprior to movement of either of said members, pivotal movement of one ofsaid levers in response to movement of one of said members beingeffective through the locking link connected thereto and said commonconnection to move the other of said locking links into a lockingposition with respect to the other of said levers to prevent movement ofthe other of said members.

8. An interlock for a pair of relatively movable members operable tolock one of said members against movement in response to movement of theother of said members which comprises apair of levers respectivelyhaving a pivot mounting and a connection with one of said members sothat 10 movement of either of said members will impart pivotal movementtoone of said levers, said pivot mountings being located at spacedpoints, .said levers extending toward each other and in overlappingrelation I from their respective pivot mountings and having end pointspositioned on opposite sides of a center-line between said pivotmountings, a pair of locking links, each of said end points having oneof said locking links pivotally connected thereto, and a flat leafspring positioned between and mounted for flexing movement toward andaway from said pivot mountings, each of said links being provided with aV-shaped notch, said spring having knife edge projecting into both ofsaid notches to provide a common connection for said links about whichthey may move angularly relative to each other, said common connectionbeing located substantially centrally of said pivot mountings prior tomovement of either of said members, pivotal movement of one of saidlevers in response to movement of one of said members being effectivethrough the locking link connected thereto and said common connection tomove the other of said locking links into a locking position withrespect to the other of said levers to prevent movement of the other ofsaid members.

9. An interlocking mechanism for a pair of levers for locking one leverupon movement of the other which comprises a pair of levers respectivelyhaving a pivot mounting, said pivot mountings being spaced from eachother, said levers extending toward each other and in overlappingrelation from their respective pivot mountings and having end pointspositioned on opposite sides of a center-line between saidpivotmountings, a pair of locking links, each of said end points havingone of said links pivotally connected thereto, and a flat leaf springmounted between said pivot mountings for flexing movement toward andaway from said pivot mountings, each of said locking links having aV-shaped notch formed therein, said spring having a knifeedge projectinginto said notches to provide a common connection between said linksabout which said links may move angularly relative to each other, saidcommon connection being normally located substantially centrally of saidpivot mountings prior to pivotal movement of either of said switches,pivotal movement of one of said levers being effective through thelocking link connected thereto and said common connection to move theother of said locking links into a locking position with respect to theother of said levers to prevent operation of the other of said levers.

10. An interlocking mechanism for a pair of levers for locking one leverupon movement of the other which comprises a pair of levers respectivelyhaving a pivot mounting, said levers being positioned side-by-side andhaving their pivot mountings spaced from eachother, a flat leafspringextending transversely of said levers and mounted for flexingmovement toward and away iromsaid pivot mountings, each of said levershaving a locking link pivotally connected thereto, each of said lockinglinks having a V-.

shaped notch formed therein, said flat leaf spring having a knife edgeextending into said notches to provide a, common connection about whichsaid locking links may move relatively to each other, movement of one ofsaid levers being effective through the link connected thereto to flexsaid leaf spring, flexing movement of said spring being effective topivot the other of said links into 11 a locking position with respect tothe other of said levers to prevent operation of the other of saidlevers.

OWEN L. TAYLOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 12 UNITED STATES PATENTS Name Date Langley Nov. 17, 1914 AlbersOct. 10, 1916 Lull Dec. 26, 1922 Wilms Feb. 15, 1938 Ellis May 23, 1944Bellon Oct. 3, 1944

